Asymmetric Hosts With Triaryl Silane Side Chains

ABSTRACT

Novel asymmetric host compounds containing an electron-transport moiety, a hole-transport moiety, an aromatic spacer, and a triaryl silane group are provided. These compounds are useful materials that can be incorporated into OLED devices.

The claimed invention was made by, on behalf of, and/or in connection with one or more of the following parties to a joint university corporation research agreement: Regents of the University of Michigan, Princeton University, The University of Southern California, and the Universal Display Corporation. The agreement was in effect on and before the date the claimed invention was made, and the claimed invention was made as a result of activities undertaken within the scope of the agreement.

FIELD OF THE INVENTION

The present invention relates to molecules containing an electron-transport moiety, a hole-transport moiety, a spacer moiety, and a triaryl silane group. These molecules are useful as host compounds in phosphorescent OLEDs.

BACKGROUND

Opto-electronic devices that make use of organic materials are becoming increasingly desirable for a number of reasons. Many of the materials used to make such devices are relatively inexpensive, so organic opto-electronic devices have the potential for cost advantages over inorganic devices. In addition, the inherent properties of organic materials, such as their flexibility, may make them well suited for particular applications such as fabrication on a flexible substrate. Examples of organic opto-electronic devices include organic light emitting devices (OLEDs), organic phototransistors, organic photovoltaic cells, and organic photodetectors. For OLEDs, the organic materials may have performance advantages over conventional materials. For example, the wavelength at which an organic emissive layer emits light may generally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage is applied across the device. OLEDs are becoming an increasingly interesting technology for use in applications such as flat panel displays, illumination, and backlighting. Several OLED materials and configurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and 5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full color display. Industry standards for such a display call for pixels adapted to emit particular colors, referred to as “saturated” colors. In particular, these standards call for saturated red, green, and blue pixels. Color may be measured using CIE coordinates, which are well known to the art.

One example of a green emissive molecule is tris(2-phenylpyridine) iridium, denoted Ir(ppy)₃, which has the following structure:

In this, and later figures herein, we depict the dative bond from nitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as well as small molecule organic materials that may be used to fabricate organic opto-electronic devices. “Small molecule” refers to any organic material that is not a polymer, and “small molecules” may actually be quite large. Small molecules may include repeat units in some circumstances. For example, using a long chain alkyl group as a substituent does not remove a molecule from the “small molecule” class. Small molecules may also be incorporated into polymers, for example as a pendent group on a polymer backbone or as a part of the backbone. Small molecules may also serve as the core moiety of a dendrimer, which consists of a series of chemical shells built on the core moiety. The core moiety of a dendrimer may be a fluorescent or phosphorescent small molecule emitter. A dendrimer may be a “small molecule,” and it is believed that all dendrimers currently used in the field of OLEDs are small molecules.

As used herein, “top” means furthest away from the substrate, while “bottom” means closest to the substrate. Where a first layer is described as “disposed over” a second layer, the first layer is disposed further away from substrate. There may be other layers between the first and second layer, unless it is specified that the first layer is “in contact with” the second layer. For example, a cathode may be described as “disposed over” an anode, even though there are various organic layers in between.

As used herein, “solution processible” means capable of being dissolved, dispersed, or transported in and/or deposited from a liquid medium, either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed that the ligand directly contributes to the photoactive properties of an emissive material. A ligand may be referred to as “ancillary” when it is believed that the ligand does not contribute to the photoactive properties of an emissive material, although an ancillary ligand may alter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled in the art, a first “Highest. Occupied Molecular Orbital” (HOMO) or “Lowest Unoccupied Molecular Orbital” (LUMO) energy level is “greater than” or “higher than” a second HOMO or LUMO energy level if the first energy level is closer to the vacuum energy level. Since ionization potentials (IP) are measured as a negative energy relative to a vacuum level, a higher HOMO energy level corresponds to an IP having a smaller absolute value (an IP that is less negative). Similarly, a higher LUMO energy level corresponds to an electron affinity (EA) having a smaller absolute value (an EA that is less negative). On a conventional energy level diagram, with the vacuum level at the top, the LUMO energy level of a material is higher than the HOMO energy level of the same material. A “higher” HOMO or LUMO energy level appears closer to the top of such a diagram than a “lower” HOMO or LUMO energy level.

As used herein, and as would be generally understood by one skilled in the art, a first work function is “greater than” or “higher than” a second work function if the first work function has a higher absolute value. Because work functions are generally measured as negative numbers relative to vacuum level, this means that a “higher” work function is more negative. On a conventional energy level diagram, with the vacuum level at the top, a “higher” work function is illustrated as further away from the vacuum level in the downward direction. Thus, the definitions of HOMO and LUMO energy levels follow a different convention than work functions.

More details on OLEDs, and the definitions described above, can be found in U.S. Pat. No. 7,279,704, which is incorporated herein by reference in its entirety.

SUMMARY OF THE INVENTION

In one aspect, a compound having the formula:

L₁-L₂-L₃  Formula I

is provided. In the compound of Formula I, L₁ is selected from the group consisting of carbazole, azacarbazole, triphenylene, aza-triphenylene and combinations thereof, L₂ is selected from the group consisting of phenyl, pyridine, pyrazine, triazine and combinations thereof; and L₃ is selected from the group consisting of dibenzofuran, dibenzothiophene, azadibenzofuran, azadibenzothiophene, dibenzoselenophene, azadibenzoselenophene, and combinations thereof. At least one of L₁ to L₃ is substituted by at least one SiAr₁Ar₂Ar₃ group, where Ar₁ to Ar₃ are independently selected from aryl or heteroaryl groups. Each of L₁ to L₃ is optionally substituted with a group selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof. Any optional substitution on L₁ and L₃ can be fused to L₁ and L₃ respectively, whereas any optional substitution on L₂ is unfused.

In one aspect, each of L₁ to L₃ is optionally substituted with a group selected from the group consisting of hydrogen, deuterium, aryl, heteroaryl, or combinations thereof. In one aspect, each of L₁ to L₃ is substituted with hydrogen.

In one aspect, L₁ is selected from the group consisting of:

In one aspect, X₁ to X₁₉ are independently CR or N, wherein R is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In one aspect, L₁ is selected from the group consisting of

wherein R is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfanyl, sulfonyl, phosphino, and combinations thereof.

In one aspect, L₂ is selected from the group consisting of:

In one aspect, L₃ is selected from the group consisting of:

wherein X₁ to X₁₀ are independently CR or N, Y₁ and Y₂ are independently O, S, or Se, and R is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In one aspect, L₃ is selected from the group consisting of:

In one aspect, Ar₁ to Ar₃ are selected from the group consisting of phenyl, biphenyl, pyridyl, naphthyl, and combinations thereof. In one aspect, Ar₁, Ar₂, and Ar₃ are phenyl.

In one aspect, L₃ contains dibenzothiophene. In one aspect, L₃ contains dibenzofuran.

In one aspect, L₂ contains phenyl. In one aspect, L₂ contains a biphenyl. In one aspect, L₂ contains a terphenyl.

In one aspect, L₁ contains carbazole. In one aspect, L₁ contains triphenylene.

In one aspect, the compound is selected from the group consisting of Compound 1-Compound 18.

In one aspect, a first device is provided. The first device comprises an organic light emitting device, further comprising an anode, a cathode, and an organic layer, disposed between the anode and the cathode, comprising a compound having the formula:

L₁-L₂-L₃  Formula I

In the compound of Formula I, L₁ is selected from the group consisting of carbazole, azacarbazole, triphenylene, aza-triphenylene and combinations thereof, L₂ is selected from the group consisting of phenyl, pyridine, pyrazine, triazine and combinations thereof, and L₃ is selected from the group consisting of dibenzofuran, dibenzothiophene, azadibenzofuran, azadibenzothiophene, dibenzoselenophene, azadibenzoselenophene, and combinations thereof. At least one of L₁ to L₃ is substituted by at least one SiAr₁Ar₂Ar₃ group, where Ar₁ to Ar₃ are independently selected from aryl or heteroaryl groups. Each of L₁ to L₃ is optionally substituted with a group selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof. Any optional substitution on L₁ and L₃ can be fused to L₁ and L₃ respectively, whereas any optional substitution on L₂ is unfused.

In one aspect, the organic layer is an emissive layer and the compound of Formula I is a host.

In one aspect, the first device further comprises a first dopant material that is an emissive dopant comprising a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of:

wherein R_(a), R_(b), R_(c) and R_(d) may represent mono, di, tri, or tetra substitution, or no substitution, and R_(a), R_(b), R_(c), and R_(d) are independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein two adjacent substituents of R_(a), R_(b), R_(c), and R_(d) are optionally joined to form a fused ring or form a multidentate ligand.

In one aspect, the organic layer is a non-emissive layer. In one aspect, the organic layer is a first organic layer, and the device further comprises a second organic layer that is a non-emissive layer and the compound having Formula I is a material in the second organic layer.

In one aspect, the second organic layer is a blocking layer and the compound having Formula I is a blocking material in the second organic layer. In one aspect, the first device is a consumer product. In one aspect, the first device is an organic light-emitting device. In one aspect, the first device comprises a lighting panel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does not have a separate electron transport layer.

FIG. 3 shows an exemplary device configuration incorporating compounds of Formula I.

FIG. 4 shows an exemplary compound according to Formula I.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed between and electrically connected to an anode and a cathode. When a current is applied, the anode injects holes and the cathode injects electrons into the organic layer(s). The injected holes and electrons each migrate toward the oppositely charged electrode. When an electron and hole localize on the same molecule, an “exciton,” which is a localized electron-hole pair having an excited energy state, is formed. Light is emitted when the exciton relaxes via a photoemissive mechanism. In some cases, the exciton may be localized on an excimer or an exciplex. Non-radiative mechanisms, such as thermal relaxation, may also occur, but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from their singlet states (“fluorescence”) as disclosed, for example, in U.S. Pat. No. 4,769,292, which is incorporated by reference in its entirety. Fluorescent emission generally occurs in a time frame of less than 10 nanoseconds.

More recently, OLEDs having emissive materials that emit light from triplet states (“phosphorescence”) have been demonstrated. Baldo et al., “Highly Efficient Phosphorescent Emission from Organic Electraluminescent Devices,” Nature, vol. 395, 151-154, 1998; (“Baldo-I”) and Baldo et al., “Very high-efficiency green organic light-emitting devices based on electrophosphorescence,” Appl. Phys. Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporated by reference in their entireties. Phosphorescence is described in more detail in U.S. Pat. No. 7,279,704 at cols. 5-6, which are incorporated by reference.

FIG. 1 shows an organic light emitting device 100. The figures are not necessarily drawn to scale. Device 100 may include a substrate 110, an anode 115, a hole injection layer 120, a hole transport layer 125, an electron blocking layer 130, an emissive layer 135, a hole blocking layer 140, an electron transport layer 145, an electron injection layer 150, a protective layer 155, a cathode 160, and a barrier layer 170. Cathode 160 is a compound cathode having a first conductive layer 162 and a second conductive layer 164. Device 100 may be fabricated by depositing the layers described, in order. The properties and functions of these various layers, as well as example materials, are described in more detail in U.S. Pat. No. 7,279,704 at cols. 6-10, which are incorporated by reference.

More examples for each of these layers are available. For example, a flexible and transparent substrate-anode combination is disclosed in U.S. Pat. No. 5,844,363, which is incorporated by reference in its entirety. An example of a p-doped hole transport layer is m-MTDATA doped with F.sub.4-TCNQ at a molar ratio of 50:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. Examples of emissive and host materials are disclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which is incorporated by reference in its entirety. An example of an n-doped electron transport layer is BPhen doped with Li at a molar ratio of 1:1, as disclosed in U.S. Patent Application Publication No. 2003/0230980, which is incorporated by reference in its entirety. U.S. Pat. Nos. 5,703,436 and 5,707,745, which are incorporated by reference in their entireties, disclose examples of cathodes including compound cathodes having a thin layer of metal such as Mg:Ag with an overlying transparent, electrically-conductive, sputter-deposited ITO layer. The theory and use of blocking layers is described in more detail in U.S. Pat. No. 6,097,147 and U.S. Patent Application Publication No. 2003/0230980, which are incorporated by reference in their entireties. Examples of injection layers are provided in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety. A description of protective layers may be found in U.S. Patent Application Publication No. 2004/0174116, which is incorporated by reference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210, a cathode 215, an emissive layer 220, a hole transport layer 225, and an anode 230. Device 200 may be fabricated by depositing the layers described, in order. Because the most common OLED configuration has a cathode disposed over the anode, and device 200 has cathode 215 disposed under anode 230, device 200 may be referred to as an “inverted” OLED. Materials similar to those described with respect to device 100 may be used in the corresponding layers of device 200. FIG. 2 provides one example of how some layers may be omitted from the structure of device 100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided by way of non-limiting example, and it is understood that embodiments of the invention may be used in connection with a wide variety of other structures. The specific materials and structures described are exemplary in nature, and other materials and structures may be used. Functional OLEDs may be achieved by combining the various layers described in different ways, or layers may be omitted entirely, based on design, performance, and cost factors. Other layers not specifically described may also be included. Materials other than those specifically described may be used. Although many of the examples provided herein describe various layers as comprising a single material, it is understood that combinations of materials, such as a mixture of host and dopant, or more generally a mixture, may be used. Also, the layers may have various sublayers. The names given to the various layers herein are not intended to be strictly limiting. For example, in device 200, hole transport layer 225 transports holes and injects holes into emissive layer 220, and may be described as a hole transport layer or a hole injection layer. In one embodiment, an OLED may be described as having an “organic layer” disposed between a cathode and an anode. This organic layer may comprise a single layer, or may further comprise multiple layers of different organic materials as described, for example, with respect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used, such as OLEDs comprised of polymeric materials (PLEDs) such as disclosed in U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated by reference in its entirety. By way of further example, OLEDs having a single organic layer may be used. OLEDs may be stacked, for example as described in U.S. Pat. No. 5,707,745 to Forrest et al, which is incorporated by reference in its entirety. The OLED structure may deviate from the simple layered structure illustrated in FIGS. 1 and 2. For example, the substrate may include an angled reflective surface to improve out-coupling, such as a mesa structure as described in U.S. Pat. No. 6,091,195 to Forrest et al., and/or a pit structure as described in U.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated by reference in their entireties.

Unless otherwise specified, any of the layers of the various embodiments may be deposited by any suitable method. For the organic layers, preferred methods include thermal evaporation, ink-jet, such as described in U.S. Pat. Nos. 6,013,982 and 6,087,196, which are incorporated by reference in their entireties, organic vapor phase deposition (OVPD), such as described in U.S. Pat. No. 6,337,102 to Forrest et al., which is incorporated by reference in its entirety, and deposition by organic vapor jet printing (OVJP), such as described in U.S. patent application Ser. No. 10/233,470, which is incorporated by reference in its entirety. Other suitable deposition methods include spin coating and other solution based processes. Solution based processes are preferably carried out in nitrogen or an inert atmosphere. For the other layers, preferred methods include thermal evaporation. Preferred patterning methods include deposition through a mask, cold welding such as described in U.S. Pat. Nos. 6,294,398 and 6,468,819, which are incorporated by reference in their entireties, and patterning associated with some of the deposition methods such as ink-jet and OVJD. Other methods may also be used. The materials to be deposited may be modified to make them compatible with a particular deposition method. For example, substituents such as alkyl and aryl groups, branched or =branched, and preferably containing at least 3 carbons, may be used in small molecules to enhance their ability to undergo solution processing. Substituents having 20 carbons or more may be used, and 3-20 carbons is a preferred range. Materials with asymmetric structures may have better solution processibility than those having symmetric structures, because asymmetric materials may have a lower tendency to recrystallize. Dendrimer substituents may be used to enhance the ability of small molecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the present invention may further optionally comprise a barrier layer. One purpose of the barrier layer is to protect the electrodes and organic layers from damaging exposure to harmful species in the environment including moisture, vapor and/or gases, etc. The barrier layer may be deposited over, under or next to a substrate, an electrode, or over any other parts of a device including an edge. The barrier layer may comprise a single layer, or multiple layers. The barrier layer may be formed by various known chemical vapor deposition techniques and may include compositions having a single phase as well as compositions having multiple phases. Any suitable material or combination of materials may be used for the barrier layer. The barrier layer may incorporate an inorganic or an organic compound or both. The preferred barrier layer comprises a mixture of a polymeric material and a non-polymeric material as described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos. PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporated by reference in their entireties. To be considered a “mixture”, the aforesaid polymeric and non-polymeric materials comprising the barrier layer should be deposited under the same reaction conditions and/or at the same time. The weight ratio of polymeric to non-polymeric material may be in the range of 95:5 to 5:95. The polymeric material and the non-polymeric material may be created from the same precursor material. In one example, the mixture of a polymeric material and a non-polymeric material consists essentially of polymeric silicon and inorganic silicon.

Devices fabricated in accordance with embodiments of the invention may be incorporated into a wide variety of consumer products, including flat panel displays, computer monitors, medical monitors, televisions, billboards, lights for interior or exterior illumination and/or signaling, heads up displays, fully transparent displays, flexible displays, laser printers, telephones, cell phones, personal digital assistants (PDAs), laptop computers, digital cameras, camcorders, viewfinders, micro-displays, vehicles, a large area wall, theater or stadium screen, or a sign. Various control mechanisms may be used to control devices fabricated in accordance with the present invention, including passive matrix and active matrix. Many of the devices are intended for use in a temperature range comfortable to humans, such as 18 degrees C. to 30 degrees C., and more preferably at room temperature (20-25 degrees C.).

The materials and structures described herein may have applications in devices other than OLEDs. For example, other optoelectronic devices such as organic solar cells and organic photodetectors may employ the materials and structures. More generally, organic devices, such as organic transistors, may employ the materials and structures.

The terms halo, halogen, alkyl, cycloalkyl, alkenyl, alkynyl, arylkyl, heterocyclic group, aryl, aromatic group, and heteroaryl are known to the art, and are defined in U.S. Pat. No. 7,279,704 at cols. 31-32, which are incorporated herein by reference.

In one embodiment, a compound having the formula:

L₁-L₂-L₃  Formula I

is provided. In the compound of Formula I, L₁ is selected from the group consisting of carbazole, azacarbazole, triphenylene, aza-triphenylene and combinations thereof, L₂ is selected from the group consisting of phenyl, pyridine, pyrazine, triazine and combinations thereof, and L₃ is selected from the group consisting of dibenzofuran, dibenzothiophene, azadibenzofuran, azadibenzothiophene, dibenzoselenophene, azadibenzoselenophene, and combinations thereof. At least one of L₁ to L₃ is substituted by at least one SiAr₁Ar₂Ar₃ group, where Ar₁ to Ar₃ are independently selected from aryl or heteroaryl groups. Each of L₁ to L₃ is optionally substituted with a group selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof. Any optional substitution on L₁ and L₃ can be fused to L₁ and L₃ respectively, whereas any optional substitution on L₂ is unfused.

In L₂, the fragments listed above can appear more than once and in any combination, so that, for example, L₂ can comprise two phenyl units (i.e. biphenyl), three phenyl units (i.e. terphenyl), two pyridines (i.e. bipyridine), a phenyl and a pyridine, etc. The groups in L₁, L₂, and L₃ can have multiple attachment points connecting them to other fragments.

The “aza” designation in the fragments described above, i.e. aza-dibenzofuran, aza-dibenzonethiophene, etc. means that one or more of the C—H groups in the respective fragment can be replaced by a nitrogen atom, for example, and without any limitation, azatriphenylene encompasses both dibenzo[fh]quinoxaline and dibenzo[fh]quinoline. One of ordinary skill in the art can readily envision other nitrogen analogs of the aza-derivatives described above, and all such analogs are intended to be encompassed by the terms as set forth herein.

It is to be understood that when a molecular fragment is described as being a substituent or otherwise attached to another moiety, its name may be written as if it were a fragment (e.g. naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g. naphthalene, dibenzofurna). As used herein, these different ways of designating a substituent or attached fragment are considered to be equivalent.

The term “fused,” as used herein to refer to substituents on L_(I), L₂, or L₃ means that the substitution on L₁, L₂, or L₃ is also attached to least at one other ring-atom on the ring bearing that substitution. The term “unfused,” as used herein to refer to substituents on L₁, L₂, or L₃ means that the substitution on L₁, L₂, or L₃ is not attached to any other ring-atom in the ring bearing that substitution.

It has been discovered that incorporation of both electron- and hole-transport moieties into one compound fine-tunes the energy levels, facilitates charge injection from adjacent layers to suppress driving voltage, and balances electron/hole fluxes and modulates charge trapping by the emitter dopant to achieve an expanded recombination zone. The L₂ spacer provides one additional region of substitution to further adjust the molecular assembly and charge transport properties. The triarylsilyl groups alleviate the undesirable intermolecular stacking, which not only retains high triplet energy in the solid state and effectively reduces quenching but also suppresses crystallization and improves film quality. The unique synergistic combination of all these properties is highly beneficial for host materials used in high-efficiency and stable phosphorescent OLED. Furthermore, the proposed compounds are soluble in common solvents such as xylene and toluene, amenable for solution processing which is highly desirable for potential low cost fabrication.

In one embodiment, each of L₁ to L₃ is optionally substituted with a group selected from the group consisting of hydrogen, deuterium, aryl, heteroaryl, or combinations thereof. In one embodiment, each of L₁ to L₃ is substituted with hydrogen.

In one embodiment, L₁ is selected from the group consisting of:

X₁ to X₁₉ are independently CR or N, wherein R is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In one embodiment, L₁ is selected from the group consisting of:

wherein R is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In any of the fragments disclosed herein, a dashed line indicates that that particular fragment can be attached at any position or positions on that fragment that has an open valence and is capable of forming a bond or bonds.

In one embodiment, L₂ is selected from the group consisting of:

In one embodiment, L₃ is selected from the group consisting of

wherein X₁ to X₁₀ are independently CR or N, Y₁ and Y₂ are independently O, S, or Se, and R is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfonyl, sulfonyl, phosphino, and combinations thereof.

In one embodiment, L₃ is selected from the group consisting of:

In one embodiment, Ar₁ to Ar₃ are selected from the group consisting of phenyl, biphenyl, pyridyl, naphthyl, and combinations thereof. In one embodiment, Ar₁, Ar₂, and Ar₃ are phenyl.

In one embodiment, L₃ contains dibenzothiophene. In one embodiment, L₃ contains dibenzofuran.

In one embodiment, L₂ contains phenyl. In one embodiment, L₂ contains a biphenyl. In one embodiment, L₂ contains a terphenyl.

In one embodiment, L₁ contains carbazole. In one embodiment, L₁ contains triphenylene.

In one embodiment, the compound is selected from the group consisting of Compound 1-Compound 18.

In one embodiment, a first device is provided. The first device comprises an organic light emitting device, further comprising an anode, a cathode, and an organic layer, disposed between the anode and the cathode, comprising a compound having the formula:

L₁-L₂-L₃  Formula I

In the compound of Formula I, L₁ is selected from the group consisting of carbazole, azacarbazole, triphenylene, aza-triphenylene and combinations thereof, L₂ is selected from the group consisting of phenyl, pyridine, pyrazine, triazine and combinations thereof, and L₃ is selected from the group consisting of dibenzofuran, dibenzothiophene, azadibenzofuran, azadibenzothiophene, dibenzoselenophene, azadibenzoselenophene, and combinations thereof. At least one of L₁ to L₃ is substituted by at least one SiAr₁Ar₂Ar₃ group, where Ar₁ to Ar₃ are independently selected from aryl or heteroaryl groups. Each of L₁ to L₃ is optionally substituted with a group selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof. Any optional substitution on L₁ and L₃ can be fused to L₁ and L₃ respectively, whereas any optional substitution on L₂ is unfused.

In one embodiment, the organic layer is an emissive layer and the compound of Formula I is a host.

In one embodiment, the first device further comprises a first dopant material that is an emissive dopant comprising a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of

wherein R_(a), R_(b), R_(c), and R_(d) may represent mono, di, tri, or tetra substitution, or no substitution, and R_(a), R_(b), R_(c), and R_(d) are independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof; and wherein two adjacent substituents of R_(a), R_(b), R_(c), and R_(d) are optionally joined to form a fused ring or form a multidentate ligand.

In one embodiment, the organic layer is a non-emissive layer. In one embodiment, the organic layer is a first organic layer, and the device further comprises a second organic layer that is a non-emissive layer and the compound having Formula I is a material in the second organic layer.

In one embodiment, the second organic layer is a blocking layer and the compound having Formula I is a blocking material in the second organic layer. In one embodiment, the first device is a consumer product. In one embodiment, the first device is an organic light-emitting device. In one embodiment, the first device comprises a lighting panel.

Device Examples

All example devices were fabricated by high vacuum (<10⁻⁷ Torr) thermal evaporation (VTE). The anode electrode is 800 Å of indium tin oxide (ITO). The cathode consisted of 10 Å of LiF followed by 1,000 Å of Al. All devices are encapsulated with a glass lid sealed with an epoxy resin in a nitrogen glove box (<1 ppm of H₂O and O₂) immediately after fabrication, and a moisture getter was incorporated inside the package.

The organic stack of the OLED device used in the Examples and Comparative Device Examples has the following structure: from the ITO surface, 100 Å of LG101 (purchased from LG Chem) as the hole injection layer, 300 Å of NPD as the hole transporting layer (HTL), 300 or 400 Å of Compounds 1, 5 or 9, or Comparative Compounds 1 or 2 doped with 20 wt % of Dopant as the emissive layer (EML), 50 Å of Compound BL as the Blocking Layer (BL) and 400 Å of Alq as the ETL. An exemplary device is depicted in the schematic in FIG. 3.

The structures of the materials used in the devices are as follows:

Table 1 summarizes the performance data of phosphorescent OLED devices based on Compounds 1, 5 and 9 vs. Comparative Compounds 1 and 2. The luminous efficiency (LE), external quantum efficiency (EQE) and power efficiency (PE) were measured at 1000 nits. Compared to the device based on compounds without triarylsilane group, i.e., Comparative Compound 2, the devices based on compounds containing triarylsilane group, i.e., Compound 1 and Comparative Compound 1, exhibit improved efficiency. This could be attributed to the successful suppression of emission quenching due to the retention of high triplet energy of host materials containing triarylsilane groups (Compound 1 and Comparative Compound 1). It is noted that the efficiency of devices based on Compounds 1, 5 and 9 is further improved compared to that based on Comparative Compound 1. Although both Compounds 1, 5 and 9 and Comparative Compound 1 contain triarylsilyl group, Compounds 1, 5 and 9 have the additional feature of an asymmetric structure. By “asymmetric structure” it is meant that the groups L₁ and L₃ are different, and have different electronic properties. This asymmetric structure provides the opportunity to achieve more balanced electron/hole fluxes in OLED devices, leading to expanded recombination zone. A broader recombination zone improves device efficiency by reducing concentration quenching.

Therefore, the compounds of Formula 1 integrates the advantages of both triarylsilyl groups and asymmetric structure, and have demonstrated as superior host materials for phosphorescent OLEDs.

TABLE 1 Comparison example EML 400A At 1000 cd/m² Blocking 1931 CIE λ_(max) Voltage LE EQE PE Example Host layer x y (nm) (V) (cd/A) (%) (lm/W) Device Compound 1 Compound 0.172 0.384 474 5.5 48.2 21.6 27.3 Example 1 BL Device Compound 5 Compound 0.173 0.385 474 5.5 49.7 22.3 28.4 Example 2 BL Device Compound 9 Compound 0.175 0.391 474 5.6 48.8 21.6 27.3 Example 3 BL Comparative Comparative Compound 0.174 0.388 474 5.9 45.5 20.2 24.1 Device compound 1 BL Example 1 Comparative Comparative Compound 0.182 0.399 474 7.1 39.1 17.0 17.4 Device compound 2 BL Example 2 Combination with Other Materials

The materials described herein as useful for a particular layer in an organic light emitting device may be used in combination with a wide variety of other materials present in the device. For example, emissive dopants disclosed herein may be used in conjunction with a wide variety of hosts, transport layers, blocking layers, injection layers, electrodes and other layers that may be present. The materials described or referred to below are non-limiting examples of materials that may be useful in combination with the compounds disclosed herein, and one of skill in the art can readily consult the literature to identify other materials that may be useful in combination.

HIL/HTL:

A hole injecting/transporting material to be used in the present invention is not particularly limited, and any compound may be used as long as the compound is typically used as a hole injecting/transporting material. Examples of the material include, but not limit to: a phthalocyanine or porphryin derivative; an aromatic amine derivative; an indolocarbazole derivative; a polymer containing fluorohydrocarbon; a polymer with conductivity dopants; a conducting polymer, such as PEDOT/PSS; a self-assembly monomer derived from compounds such as phosphonic acid and sliane derivatives; a metal oxide derivative, such as MoO_(x); a p-type semiconducting organic compound, such as 1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, and a cross-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, but not limit to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; group consisting aromatic heterocyclic compounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and group consisting 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Wherein each Ar is further substituted by a substituent selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, and combinations thereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the group consisting of:

k is an integer from 1 to 20; X¹ to X⁸ is C (including CH) or N; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or FITL include, but not limit to the following general formula:

M is a metal, having an atomic weight greater than 40; (Y¹-Y²) is a bidentate ligand, Y¹ and Y² are independently selected from C, N, O, P, and S; L is an ancillary ligand; m is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and m+n is the maximum number of ligands that may be attached to the metal.

In one aspect, (Y¹-Y²) is a 2-phenylpyridine derivative.

In another aspect, (Y¹-Y²) is a carbene ligand.

In another aspect, M is selected from Ir, Pt, Os, and Zn.

In a further aspect, the metal complex has a smallest oxidation potential in solution vs. Fc⁺/Fc couple less than about 0.6 V.

Host:

The light emitting layer of the organic EL device of the present invention preferably contains at least a metal complex as light emitting material, and may contain a host material using the metal complex as a dopant material. Examples of the host material are not particularly limited, and any metal complexes or organic compounds may be used as long as the triplet energy of the host is larger than that of the dopant. While the Table below categorizes host materials as preferred for devices that emit various colors, any host material may be used with any dopant so long as the triplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have the following general formula:

M is a metal; (Y³-Y⁴) is a bidentate ligand, Y³ and Y⁴ are independently selected from C, N, O, P, and S; L is an ancillary ligand; m is an integer value from 1 to the maximum number of ligands that may be attached to the metal; and m+n is the maximum number of ligands that may be attached to the metal.

In one aspect, the metal complexes are:

(O—N) is a bidentate ligand, having metal coordinated to atoms O and N.

In another aspect, M is selected from Ir and Pt.

In a further aspect, (Y³-Y⁴) is a carbene ligand.

Examples of organic compounds used as host are selected from the group consisting aromatic hydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene, phenanthrene, fluorene, pyrene, chrysene, perylene, azulene; group consisting aromatic heterocyclic compounds such as dibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran, benzothiophene, benzoselenophene, carbazole, indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine, thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine; and group consisting 2 to 10 cyclic structural units which are groups of the same type or different types selected from the aromatic hydrocarbon cyclic group and the aromatic heterocyclic group and are bonded to each other directly or via at least one of oxygen atom, nitrogen atome, sulfur atom, silicon atom, phosphorus atom, boron atom, chain structural unit and the aliphatic cyclic group. Wherein each group is further substituted by a substituent selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.

In one aspect, host compound contains at least one of the following groups in the molecule:

R¹ to R⁷ is independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphine, and combinations thereof, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above.

k is an integer from 0 to 20.

X¹ to X⁸ is selected from C (including CH) or N.

Z¹ and Z² is selected from NR¹, O, or S.

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holes and/or excitons that leave the emissive layer. The presence of such a blocking layer in a device may result in substantially higher efficiencies as compared to a similar device lacking a blocking layer. Also, a blocking layer may be used to confine emission to a desired region of an OLED.

In one aspect, compound used in HBL contains the same molecule or the same functional groups used as host described above.

In another aspect, compound used in HBL contains at least one of the following groups in the molecule:

k is an integer from 0 to 20; L is an ancillary ligand, m is an integer from 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable of transporting electrons. Electron transport layer may be intrinsic (undoped), or doped. Doping may be used to enhance conductivity. Examples of the ETL material are not particularly limited, and any metal complexes or organic compounds may be used as long as they are typically used to transport electrons.

In one aspect, compound used in ETL contains at least one of the following groups in the molecule:

R¹ is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof, when it is aryl or heteroaryl, it has the similar definition as Ar's mentioned above.

Ar¹ to Ar³ has the similar definition as Ar's mentioned above.

k is an integer from 0 to 20.

X¹ to X⁸ is selected from C (including CH) or N.

In another aspect, the metal complexes used in ETL contains, but not limit to the following general formula:

(O—N) or (N—N) is a bidentate ligand, having metal coordinated to atoms O, N or N,N; L is an ancillary ligand; m is an integer value from 1 to the maximum number of ligands that may be attached to the metal.

In any above-mentioned compounds used in each layer of the OLED device, the hydrogen atoms can be partially or fully deuterated.

In addition to and/or in combination with the materials disclosed herein, many hole injection materials, hole transporting materials, host materials, dopant materials, exiton/hole blocking layer materials, electron transporting and electron injecting materials may be used in an OLED. Non-limiting examples of the materials that may be used in an OLED in combination with materials disclosed herein are listed in Table 2 below. Table 2 lists non-limiting classes of materials, non-limiting examples of compounds for each class, and references that disclose the materials.

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EXPERIMENTAL

Chemical abbreviations used throughout this document are as follows: dba is dibenzylideneacetone, EtOAc is ethyl acetate, PPh₃ is triphenylphosphine, dppf is 1,1′-bis(diphenylphosphino)ferrocene, DCM is dichlorometharie, SPhos is dicyclohexyl(2′,6′-dimethoxy-[1,1′-biphenyl]-3-yl)phosphine, THE is tetrahydrofuran.

Synthesis of Compounds

Synthesis of (3,5-dibromophenyl)triphenylsilane

Into a solution of 1,3,5-tribromobenzene (9.0 g, 28.6 mmol) in diethyl ether (200 mL) was added n-butyllithium solution in hexane (2.5 M, 12 mL, 30.6 mmol) dropwise at −78° C. The reaction was stirred at this temperature for 30 minutes before a solution of chlorotriphenylsilane (9.27 g, 31.4 mmol) in diethyl ether (90 mL) was added dropwise. The reaction mixture was stirred at −78° C. for 1 hour, and then allowed to warm to room temperature and continue to stir overnight, and finally refluxed for 2 hours. After cooling to room temperature, the solid was filtered off. Upon evaporation of the solvent, the residue was purified by column chromatography on silica gel with hexane/DCM(9/1, v/v) as eluent to yield (3,5-dibromophenyl)triphenylsilane (4.0 g, 28%) as a white solid.

Synthesis of (3-bromo-5-(dibenzo[b,d]furan-4-yl)phenyl)triphenylsilane

A solution of (3,5-dibromophenyl) triphenylsilane (4.66 g, 9.43 mmol), dibenzo[b,d]furan-4-ylboronic acid (1.00 g, 4.72 mmol), Pd(PPh₃)₄ (0.109 g, 0.094 mmol) and potassium carbonate (1.304 g, 9.43 mmol) in toluene (150 mL) and water (25 mL) was refluxed under nitrogen overnight. The organic phase was isolated, filtered and evaporated. The residue was purified by column chromatography on silica gel with hexane/DCM (4/1, v/v) as eluent to yield (3-bromo-5-(dibenzo[b,d]furan-4-yl)phenyl)triphenylsilane (1.75 g, 64% yield) as a white solid.

Synthesis of Compound 1

A solution of (3-Bromo-5-(dibenzo[b,d]furan-4-yl)phenyl)triphenylsilane (3.00 g, 5.16 mmol), 9-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-91′-carbazole (1.905 g, 5.16 mmol), Pd₂(dba)₃ (0.094 g, 0.103 mmol), SPhos (0.085 g, 0.206 mmol) and K₃PO₄ (3.56 g, 15.48 mmol) in toluene (100 mL) and water (5 mL), was refluxed under nitrogen overnight. After cooling to room temperature, the solid was filtered off. Upon evaporation of the solvent, the residue was purified by column chromatography on silica gel with hexane/DCM(4/1, v/v) as eluent, followed by column chromatography on alumina with hexane/DCM (3/1, v/v) as eluent to yield Compound 1 (1.5 g, 39% yield) as a white solid.

Synthesis of (5-bromo-3′-(dibenzo[b,d]furan-4-yl)-[1,1′-biphenyl]-3-yl)triphenylsilane

A solution of (3,5-Dibromophenyl)triphenylsilane (4.27 g, 8.64 mmol), 2-(3-(dibenzo[b,d]furan-4-yl)phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (1.6 g, 4.32 mmol), Pd(PPh₃)₄ (0.100 g, 0.086 mmol) and K₂CO₃ (1.792 g, 12.96 mmol) in toluene (100 mL) and water (10 mL) was refluxed under nitrogen overnight. After cooling to room temperature, the organic phase was isolated, and the solvent was evaporated. The residue was purified by column chromatography on silica gel with hexane/DCM (4/1 to 3/1, v/v) as eluent to yield (5-Bromo-3′-(dibenzo[b,d]furan-4-yl)[1,1′-biphenyl]-3-yl)triphenylsilane (1.3 g, 45%) as a white solid.

Synthesis of Compound 2

A solution of (5-bromo-3′-(dibenzo[b,d]furan-4-yl)[1,1′-biphenyl]-3-yl)triphenylsilane (2.17 g, 3.31 mmol), 9-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carbazole (1.35 g, 3.65 mmol), Pd₂(dba)₃ (0.061 g, 0.066 mmol), SPhos (0.054 g, 0.132 mmol) and K₃PO₄ (2.11 g, 9.94 mmol) in toluene (100 mL) and water (2 mL) was refluxed under nitrogen overnight. After cooling to room temperature, the organic phase was isolated and the solvent was evaporated. The residue was purified by column chromatography on silica gel with hexane/DCM (3/1, v/v) as eluent to yield Compound 2 (2.4 g, 88%) as a white solid.

Synthesis of 9-(3′-Bromo-5′-(triphenylsilyl)-[1,1′-biphenyl]-3-yl)-9H-carbazole

A solution of (3,5-dibromophenyl) triphenylsilane (4.02 g, 8.12 mmol), 9-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carbazole (1.500 g, 4.06 mmol), Pd(PPh₃)₄ (100 mg, 0.086 mmol), K₂CO₃ (1.123 g, 8.12 mmol) in toluene (100 mL) and water (20 mL) was refluxed under nitrogen for 24 h. After cooling to room temperature, the organic phase was isolated and the solvent was evaporated. The residue was purified by column chromatography on silica gel with hexane/DCM (9/1 to 4/1, v/v) as eluent and recrystallized from hexane/DCM (9/1,v/v) to yield 9-(3′-Bromo-5′-(triphenylsilyl)-[1,1′-biphenyl]-3-yl)-9H-carbazole (2.1 g, 79%) as white crystals.

Synthesis of Compound 5

A solution of 9-(3′-Bromo-5′-(triphenylsilyl)-[1,1′-biphenyl]-3-yl)-9H-carbazole (2.97 g, 4.52 mmol) and dibenzo[b,d]thiophen-4-ylboronic acid (1.032 g, 4.52 mmol), Pd₂(dba)₃ (0.20 g, 0.021 mmol), SPhos (0.20 g, 0.049 mmol) and K₃PO₄ (2.88 g, 13.57 mmol) in toluene (120 mL) and water (5 mL) was refluxed under nitrogen overnight. After cooling to room temperature, the organic phase was isolated and the solvent was evaporated. The residue was purified by column chromatography on silica gel with hexane/DCM (4/1, v/v) as eluent to provide Compound 5 (2.5 g, 72.5%) as a white solid.

Synthesis of (5-bromo-3′-(dibenzo[b,d]thiophen-4-yl)-[1,1′-biphenyl]-3-yl)triphenylsilane

A solution of 2-(3-(dibenzo[b,d]thiophen-4-yl)phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2.00 g, 5.18 mmol), (3,5-dibromophenyl)triphenylsilane (5.12 g, 10.35 mmol), Pd(PPh₃)₄ (0.120 g, 0.104 mmol), K₂CO₃ (2.147 g, 15.53 mmol) in toluene (100 mL) and water (20 mL) was refluxed under nitrogen overnight. After cooling to room temperature, the organic phase was isolated, and the solvent was evaporated. The residue was purified by column chromatography on silica gel with hexane/DCM (2/1 v/v) as eluent to yield (5-bromo-3′-(dibenzo[b,d]thiophen-4-yl)-[1,1′-biphenyl]-3-yl)triphenylsilane (2.8 g, 80% yield) as a white solid.

Synthesis of Compound 8

A mixture of (5-bromo-3′-(dibenzo[b,d]thiophen-4-yl)-[1,1′-biphenyl]-3-yl)triphenylsilane (1.80 g, 2.67 mmol), 9H-3,9′-bicarbazole (0.89 g, 2.67 mmol), Pd₂(dba)₃ (0.049 g, 0.053 mmol), SPhos (0.044 g, 0.107 mmol), sodium tert-butoxide (0.77 g, 8.02 mmol) in m-xylene (100 mL) was refluxed at 150° C. overnight. After cooling to room temperature, it was passed through a short plug of Celite®. Upon evaporation of the solvent, the residue was purified by column chromatography on silica gel with hexane/DCM (3/1 to 2/1, v/v) as eluent to yield Compound 8 (2.2 g, 89% yield) as a white powder.

Synthesis Compound 9

A solution of (5-bromo-3′-(dibenzo[b,d]thiophen-4-yl)-[1,1′-biphenyl]-3-yl)triphenylsilane (2.180 g, 3.31 mmol), 9-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carbazole (1.346 g, 3.65 mmol), Pd₂(dba)₃ (0.061 g, 0.066 mmol), SPhos (0.054 g, 0.132 mmol) and K₃PO₄ (2.290 g, 9.94 mmol) toluene (100 mL) and water (2 mL) was refluxed under nitrogen overnight. After cooling to room temperature, the organic phase was isolated and the solvent is evaporated. The residue was purified by column chromatography on silica gel with hexane/DCM (3/1, v/v) as eluent to yield Compound 9 (2.1 g, 77% yield) as a white solid.

Synthesis of dibenzo[b,d]furan-4-yltriphenylsilane

Dibenzo[b,d]furan (5.00 g, 29.7 mmol) was dissolved in THF (150 mL), and cooled in the CO₂/1-PrOH bath. n-Butyllithium solution in hexane (2.5 M, 12.49 mL, 31.2 mmol) was added dropwise by syringe. After addition, it was stirred at room temperature for 2 hours, and cooled again in the CO₂/1-PrOH bath. Chlorotriphenylsilane (8.77 g, 29.7 mmol) in ether (50 mL) was added dropwise into the reaction solution. The reaction was gradually warmed to room temperature and stirred overnight. After evaporation of the solvent, the crude product was purified by column chromatography on silica gel with DCM/hexane (1/9, v/v) as eluent to yield dibenzo[b,d]furan-4-yltriphenylsilane (8.2 g, 65%) as a white solid.

Synthesis of (6-iododibenzo[b,d]furan-4-yl)triphenylsilane

Dibenzo[b,d]furan-4-yltriphenylsilane (9.80 g, 22.97 mmol) was dissolved in dry THF (100 mL) and cooled in the CO₂/1-PrOH bath. n-Butyllithium in hexane (2.5 M, 12.87 mL, 32.2 mmol) was added dropwise. It was warmed to room temperature, stirred for 4 hours, and cooled again in the CO₂/1-PrOH bath, and a solution of I₂ (8.63 g, 34 mmol) in ether (50 mL) was added dropwise. The reaction mixture was warmed to room temperature, stirred for 1 hour, and quenched with an aqueous solution of NaHSO₃ (10 wt %, 100 ml). It was diluted with saturated aqueous NaCl solution, extracted with EtOAc (50 mL×3 times). The organic extracts were combined, dried over anhydrous Na₂SO₄, and the solvent was evaporated. The residue was purified by column chromatography on silica gel with hexane/EtOAc (95/5 to 90/10, v/v) as eluent to yield (6-iododibenzo[b,d]furan-4-yl)triphenylsilane (7.8 g, 62%) as a white solid.

Synthesis of (6-(3-Chlorophenyl)dibenzo[b,d]furan-4-yl)triphenylsilane

A mixture solution of (6-Iododibenzo[b,d]furan-4-yl)triphenylsilane (6.60 g, 11.95 mmol), (3-chlorophenyl)boronic acid (2.80 g, 17.92 mmol), Pd(PPh₃)₄ (0.138 g, 0.119 mmol) and K₂CO₃ (3.30 g, 23.89 mmol) in toluene (100 mL) and water (15 mL) was refluxed under nitrogen for 24 hours. After cooling to room temperature, the organic phase was isolated and the solvent was evaporated. The residue was purified by column chromatography on silica gel with hexane/DCM (4/1, v/v) as eluent to yield (6-(3-chlorophenyl)dibenzo[b,d]furan-4-yl)triphenylsilane (3.7 g, 58%) as a white solid.

Synthesis of Compound 10

A solution of (6-(3-Chlorophenyl)dibenzo[b,d]furan-4-yl)triphenylsilane (2.130 g, 3.97 mmol), 9-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-9H-carbazole (1.464 g, 3.97 mmol), Pd₂(dba)₃ (40 mg, 44 mmol), SPhos (45 mg, 109 mmol), K₃PO₄ (2.283 g, 9.91 mmol) in toluene (100 ml) and water (1 ml) was stirred under nitrogen at 100° C. for 24 h. After evaporation of the solvent, the residue was purified by column chromatography on silica gel with hexane/DCM (7/3, v/v) as eluent to yield Compound 10 (2.3 g, 78%) as a white solid.

(3-Bromo-5-(triphenylen-2-yl)phenyl)triphenylsilane

A solution of (3,5-dibromophenyl)triphenylsilane (2.20 g, 4.45 mmol), 4,4,5,5-tetramethyl-2-(triphenylen-2-yl)-1,3,2-dioxaborolane (3.15 g, 8.90 mmol), Pd(PPh₃)₄ (0.051 g, 0.045 mmol) and K₂CO₃ (1.23 g, 8.90 mmol) in toluene (100 mL) and water (20 mL) was refluxed under nitrogen overnight. After cooling to room temperature, the organic phase was isolated, filtered through a short plug of Celite® and the solvent was evaporated. The residue was purified by column chromatography on silica gel with hexane/DCM (7/3, v/v) as eluent followed by recrystallization from the same solvent to yield (3-bromo-5-(triphenylen-2-yl)phenyl)triphenylsilane (1.50 g, 52%) as a white solid.

Synthesis of Compound 12

A solution of (3-bromo-5-(triphenylen-2-yl)phenyl)triphenylsilane (3.40 g, 5.30 mmol), dibenzo[b,d]thiophen-4-ylboronic acid (1.33 g, 5.83 mmol), Pd₂(dba)₃ (0.049 g, 0.053 mmol), SPhos (0.044 g, 0.106 mmol), K₃PO₄ (3.66 g, 15.90 mmol) in toluene (100 mL) and water (1 mL) was refluxed under nitrogen overnight. The hot reaction solution was filtered through a short plug of Celite® and the solvent was evaporated. The residue was purified by column chromatography on silica gel with hexane/DCM (7/3, v/v) as eluent to yield Compound 12 (2.70 g, 68%) as a white solid.

Synthesis of (6-(3-Chlorophenyl)dibenzo[b,d]furan-4-yl)triphenylsilane

A solution of (6-iododibenzo[b,d]furan-4-yl)triphenylsilane (5.00 g, 9.05 mmol), (3-chlorophenyl) boronic acid (1.7 g, 11.3 mmol), Pd(PPh₃)₄ (0.105 g, 0.091 mmol) and K₂CO₃ (2.502 g, 18.10 mmol) in toluene (75 mL) and water (10 mL) was refluxed under nitrogen for 48 h. The organic layer was separated and the solvent was evaporated. The residue was purified by column chromatography on silica gel with hexane(EtOAc (95/5, v/v) as eluent followed by recrystallization from the same solvent to yield (6-(3-chlorophenyl)dibenzo[b,d]furan-4-yl)triphenylsilane (1.0 g, 21%) as a white solid.

Synthesis of Compound 13

A solution of (6-(3-Chlorophenyl)dibenzo[b,d]furan-4-yl)triphenylsilane (1.63 g, 3.03 mmol), 4,4,5,5-tetramethyl-2-(triphenylen-2-yl)-1,3,2-dioxaborolane (1.12 g, 3.16 mmol), Pd₂(dba)₃ (0.090 g, xx mmol) and SPhos (0.10 g, 0.24 mmol) and K₃PO₄ (2.03 g, 8.8 mmol) in toluene (100 mL) and water (1 mL) was refluxed under nitrogen overnight. After cooling to room temperature, the solid was filtered of After evaporation off the solvent, the residue was purified by column chromatography on silica gel with hexane/DCM (7/3, v/v) as eluent followed by column chromatography on C18 column with acetonitrile as eluent to yield Compound 13 (1.6 g, 72%) as a white solid.

It is understood that the various embodiments described herein are by way of example only, and are not intended to limit the scope of the invention. For example, many of the materials and structures described herein may be substituted with other materials and structures without deviating from the spirit of the invention. The present invention as claimed may therefore include variations from the particular examples and preferred embodiments described herein, as will be apparent to one of skill in the art. It is understood that various theories as to why the invention works are not intended to be limiting. 

1. A compound having the formula: L₁-L₂-L₃  Formula I; wherein L₁ is selected from the group consisting of carbazole, azacarbazole, triphenylene, aza-triphenylene and combinations thereof; wherein L₂ is selected from the group consisting of phenyl, pyridine, pyrazine, triazine and combinations thereof; wherein L₃ is selected from the group consisting of dibenzofuran, dibenzothiophene, azadibenzofuran, azadibenzothiophene, dibenzoselenophene, azadibenzoselenophene, and combinations thereof; wherein at least one of L₁ to L₃ is substituted by at least one SiAr₁Ar₂Ar₃ group; wherein Ar₁ to Ar₃ are independently selected from aryl or heteroaryl groups; wherein each of L₁ to L₃ is optionally substituted with a group selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfanyl, sulfonyl, phosphino, and combinations thereof; and wherein any optional substitution on L₁ and L₃ can be fused to L₁ and L₃ respectively; and wherein any optional substitution on L₂ is unfused.
 2. The compound of claim 1, wherein each of L₁ to L₃ is optionally substituted with a group selected from the group consisting of hydrogen, deuterium, aryl, heteroaryl, or combinations thereof.
 3. The compound of claim 1, wherein each of L₁ to L₃ is substituted with hydrogen.
 4. The compound of claim 1, wherein L₁ is selected from the group consisting of:

wherein X₁ to X₁₉ are independently CR or N; and wherein R is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.
 5. The compound of claim 1, wherein L₁ is selected from the group consisting of:

and wherein R is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfanyl, sulfonyl, phosphino, and combinations thereof.
 6. The compound of claim 1, wherein L₂ is selected from the group consisting of:


7. The compound of claim 1, wherein L₃ is selected from the group consisting of:

wherein X₁ to X₁₀ are independently CR or N; wherein Y₁ and Y₂ are independently O, S, or Se; and wherein R is selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfonyl, sulfinyl, sulfonyl, phosphino, and combinations thereof.
 8. The compound of claim 1, wherein L₃ is selected from the group consisting of:


9. The compound of claim 1, wherein Ar₁ to Ar₃ are selected from the group consisting of phenyl, biphenyl, pyridyl, naphthyl, and combinations thereof.
 10. The compound of claim 1, wherein Ar₁, Ar₂, and Ar₃ are phenyl.
 11. The compound of claim 1, wherein L₃ contains dibenzothiophene.
 12. The compound of claim 1, wherein L₃ contains dibenzofuran.
 13. The compound of claim 1, wherein L₂ contains phenyl.
 14. The compound of claim 1, wherein L₂ contains a biphenyl.
 15. The compound of claim 1, wherein L₂ contains a terphenyl.
 16. The compound of claim 1, wherein L₁ contains carbazole.
 17. The compound of claim 1, wherein L₁ contains triphenylene.
 18. The compound of claim 1, wherein the compound is selected from the group consisting of:


19. A first device comprising an organic light emitting device, further comprising: an anode; a cathode; and an organic layer, disposed between the anode and the cathode, comprising a compound having the formula: L₁-L₂-L₃  Formula I; wherein L₁ is selected from the group consisting of carbazole, azacarbazole, triphenylene, aza-triphenylene and combinations thereof; wherein L₂ is selected from the group consisting of phenyl, pyridine, pyrazine, triazine and combinations thereof; wherein L₃ is selected from the group consisting of dibenzofuran, dibenzothiophene, azadibenzofuran, azadibenzothiophene, dibenzoselenophene, azadibenzoselenophene, and combinations thereof; wherein at least one of L₁ to L₃ is substituted by at least one SiAr₁Ar₂Ar₃ group; wherein Ar₁ to Ar_(a) are independently selected from aryl or heteroaryl groups; wherein each of L₁ to L₃ is optionally substituted with a group selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfonyl, sulfonyl, phosphino, and combinations thereof; and wherein any optional substitution on L₁ and L₃ can be fused to L₁ and L₃ respectively; and wherein any optional substitution on L₂ is unfused.
 20. The first device of claim 19, wherein the organic layer is an emissive layer and the compound of Formula I is a host.
 21. The first device of claim 20, further comprising a first dopant material that is an emissive dopant comprising a transition metal complex having at least one ligand or part of the ligand if the ligand is more than bidentate selected from the group consisting of:

wherein R_(a), R_(b), R_(c), and R_(d) may represent mono, di, tri, or tetra substitution, or no substitution; wherein R_(a), R_(b), R_(c), and R_(d) are independently selected from the group consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl; heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfonyl, sulfonyl, sulfonyl, phosphino, and combinations thereof; and wherein two adjacent substituents of R_(a), R_(b), R_(c), and R_(d) are optionally joined to form a fused ring or form a multidentate ligand.
 22. The first device of claim 19, wherein the organic layer is a non-emissive layer.
 23. The first device of claim 19, wherein the organic layer is a first organic layer, and the device further comprises a second organic layer that is a non-emissive layer and the compound having Formula I is a material in the second organic layer.
 24. The first device of claim 23, wherein the second organic layer is a blocking layer and the compound having Formula I is a blocking material in the second organic layer.
 25. The first device of claim 19, wherein the first device is a consumer product.
 26. The first device of claim 19, wherein the first device is an organic light-emitting device.
 27. The first device of claim 19, wherein the first device comprises a lighting panel. 